COLLECTIONS IN ECONOMIC GEOLOGY AND METALLURGY. 45 



(G) Accretions, which are deposits formed upon the walls of the fur- 

 nace. These are assorted according to their characteristics and then go 

 to tiie shaft furnaces. 



A general view of the works is shown on PL. vi. The yard and 

 stalls for roasting the coarse sulphide ores are shown on pl. vii. The 

 interior of the shaft-furnace house at the tap-hole level is shown on 



PL. VIII. 



The collection shows a large variety of the ores, together with roasted 

 ores, the fluxes, the base bullion, the slag, the by-products of both, the 

 roasting and smelting operations, and the final products. It was pre- 

 pared by Mr. Anton Eilers, the manager of the company in ISSa-'SG. 



Ores. 



The basic oxidized ores treated at these works are almost entirely 

 obtained from the Madonna mine, Monarch, Chaffee County, Colorado. 

 The ores consist for the most part of carbonate of lead (cerussite), 

 much of it being in the form of sand, colored by iron. Occasionally 

 unaltered galena is found, and occasionally, also, the sulphate (angle- 

 site) is found. The following eighteen specimens show the different 

 varieties of ores from this mine: 



(1) Sand carbonate, consisting of a mixture of carbonate and sulphate of lead and 

 oxide of iron. This specimen represents the bulk of the ore body of the mine, (51074. ) 

 the typical analysis* of which is as follows : 



Per cent. 



Sesquioxide of iron (FejOa) 



Se.-'ijuioxide of manganese (Mn203 



Aluminii (AI2O3) 



Oxide of zinc (ZnO) 



Lime (CaO) 



Magnesia (MgO) 



Sulphate of lead (PbSOj) 



Carbonate of lead (PbCOj) 



Arsenic (As) 



Antimony (Sb) 



Copper (Cu) 



Silica (SiOj) 



Sulphuric anhydride (SO3) 



Carbonic acid (CO2) 



WatercHjO) 



Sulphur (S) 



Silver (Ag) 



32.99 

 0.93 

 ?.99 

 4.17 

 1.78 

 None. 

 12.47, 

 32. 35- 

 Faiut trace. 

 Faint trace. 

 None. 

 4.24 

 3.30 

 6.73 

 6.68 

 Trace. 

 0.023 



Remarks. 



(Fe varies from 13.0 to 33.5). 



(As silicate). 

 (CaCOs-S. 18). 



(Pb varies from 20.0 to 45.0). 



(S— 1.32.) 



Jin sulphides.) 



Or 6.8 ounces per ton (varies from 5 to 

 12 ounces per ton). 



(2) Cerussite, crypto-crystalline in structure and very pure, assaying 74 per 

 cent, of lead and 14 ounces of silver per ton. (51055.) 



(3) Cerussite, dark, showing a few crystals. This variety of ore averages by assay 

 66.5 per cent, of lead and 5.1 ounces of silver per tou. (51059.) 



"All the analyses and assays in this collection were made by Mr. Robert Sticht, the 

 chief chemist of the company, except as otherwise noted. 



